Method and apparatus for forming bushings in parts



June 5, 1962 c. H. MCSHAN 3,037,547

METHOD AND APPARATUS FOR FORMING BUSHINGS IN PARTS Filed Oct. 1, 1957 DRY POWDE ADHES AP PLICATOR IIIZW.

INVENTOR CLARENCE H. McSHAN 6W 44, @WEZML HIS ATTORNEYS,

3,037,547 Patented June 5, 1962 3,037,547 METHOD AND APPARATUS FOR FORMING BUSHINGS IN PARTS Clarence H. McShan, Great Neck, N.Y. (21 Bluff Point Road, Northport, Long Island, N.Y.) Filed Oct. 1, 1957, Ser. N0. 687,449 4 Claims. (Cl. 156423) The present invention relates to bushings and the like, and more particularly to new and improved methods and means for inserting bushings of flexible material in holes in objects such as piano action parts, for example, to form bearings in which shafts and the like may rotate substantially noiselessly.

It has been the practice for many years to use bushings of felt or other simliar fabric as bearings for the many pivoting parts in a piano action. Up to the present time, these bushings have always been inserted in piano actions by hand. Since over three hundred and fifty such bushings are used in the conventional piano action, it will be appreciated that this is a relatively costly and time-consuming operation. Further, it is difficult to secure uniform bushings in manual operations and there is considerable wastage of material caused by unsatisfactory bushings that must be rejected.

It is an object of the present invention, accordingly, to provide new and improved bushing forming methods and means of the above character that are free from the above-described deficiencies of the prior art.

Another object of the invention is to provide new and improved bushing forming methods and means of the above character enabling bushings of high quality to be made quickly at low cost.

According to the invention, bushing material such as felt in strip form is fed into a bushing former which has an entrance of relatively large size tapering down to a bore slightly smaller than the opening into which a bushing is to be fitted. The felt strip is adapted to be advanced by a mandrel movable into the bore in the bushing former and having laterally projecting portions tending to grip the adjacent felt. When properly inserted in the bushing former, the forward portion of the felt strip is formed as a cylinder and lies in the bore of the bushing former around the mandrel. By advancing the mandrel, the cylindrical forward felt portion is inserted into the opening in the object in which it is to serve as a bushing, which is positioned adjacent the bushing former and coaxially of the bore therein. After withdrawal of the mandrel, the felt portion thus advanced is cut off and the bushing thus formed may be made secure in the object by gluing or other suitable means.

Where it is desired to secure the bushing in the bore by the use of an adhesive, suitable adhesive material is applied to the side of the felt strip which will form the outside of the bushing prior to insertion of the formed strip in the opening to be bushed. Preferably, the adhesive material is applied in dry powdered form and a suitable solvent is added after the bushing has been formed to cause the latter to adhere securely to the object in which it has been inserted.

The invention may be better understood from the following detailed description of a representative embodiment, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of bushing forming apparatus constructed according to the invention;

FIG. 1A is a top view of part of the apparatus in FIG. 1 showing the coupling between the mandrel and actuator means therefor.

FIG. 2 is a bottom view partly in section of a portion of the apparatus in FIG. 1 illustrating how the felt strip is formed into a cylindrical shape;

FIG. 3 shows the cylindrical felt advanced into the opening to be bushed; and

FIG. 4 shows the cylindrical bushing in the opening to be bushed and the mandrel returned to its initial position.

Referring now to FIG. 1, typical apparatus according to the invention comprises a bushing former 10 mounted on a suitable base member 11 and having a bell-shaped opening 12 formed therein communicating, and in axial alignment with a cylindrical bore 13. The base 11 also carries a support 14 for a roll 15 of bushing material, such as felt, for example.

The felt in strip form, of width substantially equal to the outer circumference of the finished bushing and of suflicient thickness to give the desired bearing tightness, is fed from the roll 15 through conventional means 17 for applying a dry powdered adhesive material to the upper surface of the felt. The adhesive applicator means 17 may be of any conventional type capable of uniformly applying dry powdered adhesive to the upper surface of the felt as the latter is advanced towards the bushing former 11).

The felt strip 16 is adapted to be advanced by a mandrel 18 which is slidably mounted in a bearing 19 carried by a standard 20 secured on the base 11. The forward end of the mandrel 18 (FIG. 2) is preferably shaped so as to be capable of advancing the felt strip 16 with it when it is moved forwardly in translation and of being readily unscrewed from the felt strip 16 to enable the for-med bushing portion to be cut off. Preferably, the forward end of the mandrel 18 is provided with a so-called buttress spiral thread which has a front surface substantially perpendicular to the mandrel axis and a rear surface at an angle to that axis, as shown. Preferably, the edges of the thread are rounded to avoid damage to the felt in retracting the mandrel and a high polish is provided to minimize rotational friction.

The mandrel 18 is adapted to be advanced in translation by a lever arm 21 which may be pivotally mounted on the base 11 at 22. The mandrel 18 is secured to the lever arm 21 by a coupling member 23 (FIG. 1A) which prevents relative translatory motion between the two but permits free rotation of the mandrel 18 as required to advance or retract the same. Adjustable forward and rear stops 24 and 25 are provided for limiting the forward and rearward motion of the mandrel. Also, the mandrel 18 is provided with suitable means such as a handwheel 26 by means of which it may be rotated to move it rearwardly relatively to the felt strip 16, as described in greater detail herein-after.

In operation, the object 27 containing the opening 28 to be hushed, which may be a part of a conventional piano action, for example, is mounted on suitable clamping means 29 with one face closely adjacent the bushing former 1t) and with the opening 28 disposed coaxially of the bore 13. The felt strip 16 is then threaded through the adhesive applicator 17 and into the bushing former 10 with the mandrel 18 in the position shown in FIGS. 1 and 2. The lever arm 21 is then moved to the left (FIG. 1) by a handle 30 until it is brought to rest by engagement with the forward stop member 24. This causes the laterally extending threads on the forward portion of the mandrel 18 to grip the felt fibers so that the forward cylindrical portion of the felt strip 16 is advanced into the opening 28 in the part 27. In this operation the buttress thread on the mandrel forms a corresponding thread impression in the felt.

The handwheel 26 is then rotated counterclockwise to unscrew the mandrel 18 from the spiral thread impression formed in the portion of the felt strip advanced into the opening 28. The mandrel 18 moves rearwardly relatively to the felt strip as the handwheel is operated carrying the lever arm 21 with it. This movement continues until the lever arm 21 engages the stop 25. At this time, a thin bladed knife which, in practice may be a thin circular disc driven at high speed, may be inserted between the part 27 and the bushing former 10 to cut off the felt bushing that has been inserted into the opening 28. This condition is illustrated in FIG. 4 of the drawings.

It will be recalled that dry powdered adhesive was ap plied to the upper surface of the felt strip 16 in passing through the applicator 17. As a consequence, a layer of powdered adhesive will be present between the outer surface of the bushing 31 and the opening 28 in the part 27. Accordingly, if the part 27 is now removed from the clamping means 29 and the bushing 31 is moistened by a suitable solvent for the adhesive, this will result in the bushing 31 being firmly secured in the opening 28 without the body of the felt becoming hardened with the adhesive material. The bushing 31 may then be allowed to dry with its bearing pin in place.

While a number of different adhesive compositions are suitable for use in the practice of the invention, it is preferred to use a waterproof urea formaldehyde resin adhesive which is available as a water soluble powder under the trade name of Weldwood glue. Where this ma terial is used as the adhesive, the completed bushing can be secured within the opening 28 merely by moistening it by a water alcohol solution.

While bushings formed as described above are obviously secure, the use of an adhesive is not necessary. On the contrary, extended tests have shown that unglued bushings stay in place and tend to be more uniform in characteristics than those that are secured by adhesive material.

Retraction of the mandrel 18 by unscrewing it from the felt as described above is quite accurate and can be calibrated in terms of the number of turns required for proper retraction of the mandrel for a given work piece thickness (width of hearing or bushing). Therefore, the process is eminently suitable for automatic control to obtain automatic sequencing and operation of the steps described above by conventional automation techniques.

The invention thus provides a novel method and means for forming flexible bushings of the type used in piano actions, and the like. By virtue of the structure disclosed, bushings of high quality and uniformity may be inserted into the openings in parts quickly and at relatively low cost. Since the bearing tightness can be selected by controlling the width of the felt strip, it is no longer necessary to ream the finished bushings by hand to insure the proper degree of tightness.

While a specific embodiment of the invention has been described herein and illustrated in the drawings, it will be understood that modifications may be made both in the apparatus and in the procedural steps employed within the scope of the invention. The invention, therefore, is not to be limited to the specific form disclosed by way of illustration but is defined in the following claims.

I claim:

1. In apparatus for forming bushings, the combination of bushing former means having a mouth portion communicating and in axial alignment with a bore of substantially the size desired for the bushings, mandrel means movable axially of the bore in said bushing former means and adapted to cooperate therewith to form flexible material disposed lengthwise of the mandrel means and in the space between it and the bore into substantially tubular shape, and means forming forwardly and outwardly extending projections at the forward end of said mandrel means for engaging the formed flexible material to advance the same through said bore when said mandrel means is moved towards said bushing former means.

2. In apparatus for forming bushings from flexible strip material, the combination of bushing former means having a bore of substantially the size desired for the bushings and a wider mouth portion communicating with said bore, mandrel means having a threaded forward portion of a size to enter said mouth portion and bore and adapted to cooperate therewith to form flexible strip material disposed lengthwise of said mandrel means and in the space between the latter and said bore into substantially tubular shape, means mounting said mandrel means for translatory movement towards said bushing former means with at least part of said threaded forward portion in said bore to advance formed flexible strip material therethrough, and means for rotating said mandrel means about its axis to enable said threaded forward portion to be retracted relatively to the formed flexible material after advancement thereof.

3. In apparatus for forming bushings, the combination of bushing former means having a bell-shaped opening tapering to a bore of substantially the size desired for the bushings, a support for a supply of continuous flexible strip material, mandrel means having a threaded forward portion of a size to enter said bell-shaped opening and bore and adapted to cooperate therewith to form flexible strip material from said support, disposed lengthwise of said mandrel means and in the space between the latter and said bore into substantially tubular shape, means for imparting translatory movement to said mandrel means to advance said flexible strip axially of said bore, means for imparting rotational movement to said mandrel means to enable it to be retracted relatively to the formed flexible material after advancement thereof, and stop means cooperating with said mandrel means to limit forward and rearward movement thereof.

4. Apparatus as defined in claim 3 for forming bushings together with means interposed between said bushing former means and the support for the supply of flexible strip material for applying an adhesive material to one side of said strip material as it is advanced towards said bushing former means.

References Cited in the file of this patent UNITED STATES PATENTS a an? 

